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31 Cards in this Set
- Front
- Back
Contraction |
conversion of chemical energy to mechanical energy -allows locomotion, propulsion through body |
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myofibers/muscle fibers |
cells that make up skeletal muscle, large, elongted cylinders; multiple nuclei, run in parallel |
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myofibrils |
bundle up to make muscle fibers; made of myofilaments; the greater the density of myofibrils, the greater the force that can be generated |
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components of myofibrils |
myosin(thick) and actin(thin) filaments>>myosin has big head with actin-binding site and myosin atpase -actin strands have sites for myosin attachment, which are covered by tropomyosin when fiber is relaxed. |
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troponin |
attaches to tropomyosin, contains Ca2+ binding site that alter configuration. -when site is vacant, troponin stabilizes tropomyosin in blocking position -when bound, troponin initiates atwist in tropomyosin that exposes myosin head attachment sites |
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sarcomere |
repeating series of contractile segments within myofibrils |
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sliding filament model of myofiber contraction |
actin filaments pulled by myosin heads toward center of sarcomere, resulting in contraction. |
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4 step contraction cycle |
1) binding: myosin cross bridge binds to actin molecule 2) power stroke: cross bridge bends, pulling thin myoilament inward 3) detachment: cross bridge detatches at end of power stroke and returns to original conformation 4) binding cross bridge binds to more distal actin molecule; cycle repeats |
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t tubules & contraction |
-t tubules are membrane proections between muscle fibers -action potential enters fiber interior along t tubules -action potential triggers release of Ca2+ from sarcoplasmic reticulum (SR) into cyosol; myofibrils flooded in Ca2+ -Ca2+ sequestered back into SR by Ca2+ ATPase pumps when AP stimulus subsides -Ca2+ binds troponin, moving tropomosin and allowing cross bridge cycling during contraction |
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endoskeleton |
tendons attack muscle to bones for leverage |
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exoskeleton |
muscles attach directly to apodemes proecting from inner face of exoskeleton on overlying bone |
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hydrostatic skeleton |
manipulation of fluid provides for tension generation and a dynamic form of leverage |
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vertebrate v invertebrate tension control |
muscle fibers innervated by 1 motor neuron v muscle fibers innervated by more than one motor neuron |
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2 stereotyped portions |
action potential strength, muscle fiber contractile strength |
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motor unit size |
delicate movements: small motor unit; few fibers/motor unit powerful movements: large motor unit; more fibers/motor unit |
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tetanus |
smooth, sustained contraction - rapid ap firing; relaxation can't occur |
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energy storage: vert v invert |
creatine phosphate; arginine phosphate |
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fatigue |
typical stimulation produces decreased contractile response; fuel depletion(glycogen), increased adp, lactate, extracellular K+ |
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oxygen debt |
deep breathing after activity occurs; o2 is needed for energy systems (anabolism) -conversion of lactate into pyruvate and two pyruvate into glucose -replenish creatine phosphate -replenish glycogen stores |
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dark meat |
slow twitch oxidative fibers -long lateny to peak tension -high aerobic capacity; myoglobin, blood supply, mitochondira -low glycogen -high fatigue resistance |
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white meat |
fast twitch glycolitic fibers -short latency to peak tension -low aerobic capacity -low myoglobin, blood supply, mitochondira -high glycogen and low resistance to fatigue |
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effects of high intensity activities |
-increased synthesis of myosin and actin filaments -increased size and %muscle mass of fast twitch fibers |
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corticospinal motor systems |
fine motor control and conscious movement |
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brainstem motor systems |
regulation of overall body posture, involuntary movements of trunk and limbs |
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smooth muscle |
single long nucleus, no striations, does not contract all in one direction |
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smooth muscle contraction |
when ca2+ binds to calmodulin, activates myosin light chain kinase that phosphorylates myosin and promotes cross bridge cycling |
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catch state |
smooth muscle; tethered to maintain tension with low atp consumption; occurs after ACh withdrawn, serotonin relaxes catch |
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multi-unit smooth muscle |
multiple neurons stimulating same organ; phasic |
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single-unit smooth muscle |
1 neuron for entire smooth muscle, tonic with phasic "burts"; always partially contracted to some egree |
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cardiac and skeletal similarities |
striated t-tubules and SR aerobic activity |
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cardiac and smooth similarities |
self-excitable with basal tonic state interconnected by gap junctions innervated by autonomic nervous system |